1. Field
Embodiments of the present disclosure relate to key generation and issuance, and more particularly, to a technology for generating, based on user identity (ID) information, a cryptographic key such as a private key of the user.
2. Discussion of Related Art
Unlike general public-key cryptography schemes, most ID-based cryptography (IBC) schemes require a pairing operation for encryption and decryption. As an alternative, an IBC scheme using a trapdoor discrete logarithm (TDL) group has been introduced. Such a TDL-IBC scheme involves an operation which is simpler than a pairing operation when encryption/decryption is performed on a client side, and therefore may be more useful for application to devices, for example, mobile communication terminals, than other IBC schemes.
The TDL-IBC scheme generates a key using a discrete logarithm problem that is practically difficult to solve when information on the trapdoor is not known. However, the TDL-IBC scheme may require a huge amount of resources for a process of extracting a private key corresponding to a user's ID, and it may take too much time to issue the private key. This means that excessively high cost would be incurred as the number of users increases. Therefore, there is a need for a new approach to practical application of an IBC scheme which uses a discrete logarithm cyclic group such as a TDL group.